Mechanisms of fatigue crack growth in Austempered Ductile Iron

Greno, G.L; Otegui, J.L.; Boeri, Roberto Enrique

doi:10.1016/s0142-1123(98)00055-3

Cited by 82 publications

(93 citation statements)

References 9 publications

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“…As a direct result there were fewer coalescence events visible for these specimens until the failure mechanism was almost exclusively propagation controlled. It is reasonable therefore to suggest that decohesion and subsequent crack initiation is in fact sensitive to the crack tip stress intensity factor and hence the locally raised stress field experienced by the graphite nodules, fitting in with previous observations [31]. The plastic zone ahead of the advancing crack increases with increasing stress intensity factor.…”

Section: Crack Initiationsupporting

confidence: 85%

“…The angular nature of the crack initiating pores clearly provide points of stress concentration. Other authors [29,30,31] have observed initiation of this type. It is suggested that in the absence of pores and other such defects, primary initiation occurs at graphite nodules [21].…”

Section: Crack Initiationmentioning

confidence: 79%

“…Decohesion of the interface between the graphite nodules and matrix is likely to be caused by mechanical property mismatch occurring in the stress field ahead of the advancing crack, leading to the subsequent initiation of micro-cracks. Greno et al [31] identified the irregular surface of the graphite-matrix interfaces (sharp micro-notches) as high stress concentrators. These act as preferential initiation sites in the increased ΔK region in the vicinity of the advancing crack tip.…”

Section: Crack Initiationmentioning

confidence: 99%

“…Investigation of the mechanism of micro-crack initiation ahead of the advancing crack tip has been conducted by means of a 2D elastic computational model developed using the boundary element method [31]. A graphite nodule was modelled as having nucleated micro-cracks fore and aft with respect to the dominant crack at varying positions along the nodule perimeter.…”

Section: Crack Propagationmentioning

confidence: 99%

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Effects of graphite nodules on crack growth behaviour of austempered ductile iron

Stokes

Gao

Reed

2007

Materials Science and Engineering: A

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Austempered ductile iron (ADI) is a candidate material for camshafts, where however, the early stages of fatigue damage are of major concern during service. A fundamental microstructurally based assessment of the mechanisms of fatigue failure is important. An ADI microstructure austenitised at 900°C and austempered at 390°C has been investigated in detail. Crack initiation and growth behaviour was assessed under three-point bend testing conditions. Primary initiation events occurred exclusively at pores with further micro-crack initiation occurring at decohered graphite nodules in the monotonic plastic zone ahead of the advancing dominant macro-crack tip. Lifetime was however determined by propagation behaviour rather than coalescence events. The changes in the as-cast microstructure generated by this heat treatment have resulted in improved fatigue crack propagation performance due to the reduction in eutectic carbides and the relatively high quantity of retained * Corresponding author. Tel.: +44-238-059-3763; Fax: +44-238-059-3016 E-mail address: pasr1@soton.ac.uk (P.A.S. Reed) 2 austenite compared with previous studies, giving rise to greater crack path tortuousity and shielding.

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Section: Crack Initiationsupporting

confidence: 85%

Section: Crack Initiationmentioning

confidence: 79%

Section: Crack Initiationmentioning

confidence: 99%

Section: Crack Propagationmentioning

confidence: 99%

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Effects of graphite nodules on crack growth behaviour of austempered ductile iron

Stokes

Gao

Reed

2007

Materials Science and Engineering: A

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“…이러한 오스페라이트 조직을 갖는 ADI는 인장강도 가 구상흑연주철의 두 배 이상이며(850~1600 MPa), 주철에서 얻을 수 없는 높은 연신율(~13%)을 가지는 우수한 재질이다 [1][2][3]. 그러나 ADI의 기지에 포함되어 있는 흑연 노듈이 하중 을 받는 환경에서 크랙의 시발점으로 작용해 충격강도와 파괴 인성을 감소시키고 높은 마모조건의 환경에서 제품의 수명을 단축시키기 때문에 일종의 결함으로 작용한다 [4]. 이를 보완하기 위해 최근 연구자들은 ADI에 만족하지 않고 보다 우수한 소재를 얻고자 오스템퍼링된 고탄소·고규소강에 대한 연구를 진행하였다 [5][6][7].…”

Section: 서 론unclassified

Mechanical Properties of Austempered Fe-2.0wt.%Si-0.3wt.%Mn Steel with various Carbon Contents

Ha¹,

Shin²,

Lee³

et al. 2015

Journal of Korea Foundry Society

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In this study, we investigated the effect of carbon on mechanical properties with different austempering conditions of high carbon(0.7~1.3wt.%C)-2.0wt.%Si steels. The specimens were austenitized at 850, 925 and 1020 o C, and austempered at 260, 320 and 380 o C for the various period of time from 3 min to 300 min. After heat treatment, the evolution of stage I and stage II was identified with optical microscope, XRD and hardness test. When the austempering temperature was 260 o C, the microstructure consisted of the lower ausferrite while the upper ausferrite micro-structure was formed at 380 o C. As the austempering temperature increases from 260 to 380 o C, the tensile strength decreases and elongation increases. In addition, when carbon content increases, tensile strength and elongation decrease. 실험 방법2.1 용해, 주조 및 압연 본 실험에 사용된 시편의 제조를 위한 고탄소·고규소강의 용해는 대기 중에서 50 kg 용량의 고주파 유도로에서 실시하였

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